Alkylation process



Feb. 18, 1958 J, KELLY r 2,824,163

ALKYLATION PROCESS Filed July 6, 1956 A6 T IONA SEPARATOR INVENTORS JoeI Kelly Harmon M Knight ATTORNEY MM. QM

ALKYLATION PROCESS Joe T. Kelly, Dickinson, and Harmon M. Knight, LaMarque, Tex., assignors to The American Gal Company, Texas City, Tex., acorporation of Texas Application July 6, 1956, Serial No. 596,359

9 Claims. (Cl. Mil-633.44)

This invention relates to the reaction of isoparafiins or aromatichydrocarbons and olefins. More particularly it relates to the alkylationof isobutane with ethylene.

In the petroleum industry today, the octane race has placed a strain onfacilities and materials needed to make gasoline meeting present dayautomotive engine requirements. One of the remaining sources of highoctane components is the product of the alkylation of isobutane andethylene. This alkyiation is not easy to carry out, particularly on alarge scale.

An object of the invention is the alkylation of isoparatfins,particularly isobutane, with olefins, particularly ethylene. Anotherobject is the alkylation of aromatic hydrocarbons with olefins. Stillanother object is a process for polymerizing ethylene. Other objectswill become apparent in the course of the detailed description.

The alkylation of isoparafins or aromatic hydrocarbons with olefins iscarried out in the presence of a novel catalyst pair. One member of thecatalyst pair is boron tritluoride. The other member of the catalystpair is a nickel silicomolybdate hydrate, that is, a nickelsilicomolybdate salt containing water of hydration. Although the secondcomponent of the catalyst pair is spoken of as a hydrate, it is believedthat the solid member is more properly a complex of the hydrate and BFthe BB, is believed to complex with some or all of the hydrate waterpresent in the nickel silicomolybdate hydrate salt. More than the amountof BP needed to complex the water of hydration is necessary to obtainthe desired catalytic effect.

Boron trifiuoride is one member of thecatalyst pair. Commercial gradeanhydrous boron trifiuoride is suitable for use as one member of thecatalyst pair.

The other member of the catalyst pair, hereinafter spoken of as thesolid member, is nickel silicomolybdate hydrate. The salt may be used asa fine powder, as pellets, or may be supported on a solid carrier suchas alumina, charcoal, silica gel, etc.

it is necessary that the salt contain hydrate water. The anhydrous saltsdo not have any promotional effect on the activity of B1 It is notnecessary that any particular hydrate be used; apparently it isnecessary only that some water of hydration be present.

The BR and the defined salt react to form a solid material containingcomplexed BF When the salt hydrate and ER are contacted in a closedvessel, the BE; partial pressure drops very rapidly at first and thengradually approaches a constant value. It appears that a very rapidreaction between the B1 and some of the water of hydration takes place.This initially rapid reaction is then followed by a relatively slowreaction between the States Patent O 2,824,163 Patented Feb. 18, 1958remaining molecules of hydrate water and additional BF It appears thatwhen the salt hydrate is exposed to BF even in the presence ofhydrocarbon reactants, eventually all of the water of hydration willbecome associated with BF on about a 1 mole of BF per mole of hydratewater basis.

A complex of the defined salt hydrate and RE, is not an effectivecatalyst for the alkylation in the absence of free-BF Free-BP is to beunderstood as BF existing in the reaction zone which is not complexedwith the defined salt hydrate. As soon as the salt hydrate has complexedwith some BF the beneficial catalytic efiect exists. Thus free-B1 mayexist in the reaction zone, as evidenced by the formation of alkylate,even though all of the hydrate water has not been complexed. in a batchsystem, wherein less BF is present than is theoretically required tocomplex all the water of hydration present in the salt hydrate,eventually no alkylation Will occur as charge is added, since all of theBF will become complexed.

In general, the process is carried out utilizing an amount of B1 whichis in excess of that required to complex with all the hydrate waterpresent in the contacting zone, namely, in excess of about 1 mole of B1per mole of hydrate Water present. More than the minimum amount offree-B1 is beneficial, in fact, the yield of alkylate increases rapidlywith increase in the free-B1 present, up to a maximum amount. The amountof free-8P used is dependent somewhat upon the reactants themselves.However, when reacting isoparafiins and olefins, the free-8P usage isdesirably, set out on a BF to olefin weight ratio, of at least about0.2. In other words, at least about 0.2 lb. of BP per lb. of olefincharged to the alkylation Zone is desirable. About 1.5 parts by weightof BF per port of olefin charged appears to be about the desirablemaximum usage of B1 It is preferred to use between about 0.35 and 1 partby weight of free-B1 per part by weight of olefin when utilizing thelower molecular weight olefin, such as ethylene and propylene.

The process may be carried out at any temperature below the temperatureat which the salt hydrate decomposes, that is, loss of all its water ofhydration. The temperature of operation may be as low as -20 C. or evenlower. Temperatures as high as: 150 C. and even higher may be used;however, more usually the temperature of operation will be between about0 C. and C. Lower temperatures appear to favor the formation of thehydrocarbons having 6 to 7 carbon atoms. It is preferred to operate at atemperature between about 25 C. and 40 C.

Sufficient pressure is maintained on the system to keep a substantialportion of the hydrocarbons charged in the liquid state. The process maybe carried out at relatively low pressures, for example, 100 p. s. i.,or it may be carried out at elevated pressures, for example, 2000 p. s.i., or more. In general, pressures will be between about 200 and 1000 p.s. i. and preferably between about 300 and 600 p. s. i.

The contacting of the isoparaflin or aromatic hydrocarbon and the olefinin the presence of the defined catalyst pair is continued until anappreciable amount of alkylate has been formed. In batch reactions, itis possible to convert substantially 100% of the olefin by a,

. usage.

3. sufi'iciently long period of contacting. When operating in acontinuous flow system, it may be desirable to have a time of contactingsuch that substantial amounts of olefin are not converted and obtain thecomplete conversion of the olefin by a recycle operation. The time ofreaction will be determined by the type of hydrocarbons charged, theratio of isoparafiin or aromatic to olefin, the degree of mixing in thecontacting zone and the catalyst A few tests will enable one todetermine the optimum time of contacting for the particular system ofoperating conditions being tried.

The reactants in the hydrocarbon charge to the alkylation process areisoparaffin, or aromatic and olefin. The olefin contains from 2 to,about 12 carbon atoms. Examples of suitable olefins are ethylene,propylene, butene- 2, hexene and octene; in addition to these, theolefin polymers obtained from propylene and/or butylene are alsosuitable for use in the process, such as codimer, propylene trimer,propylene te tramer and butylene trimer. It is, preferred to operatewith ethylene or propylene.

The aromatic hydrocarbons must be alkylatable by the particular olefinused. It is self-evident that an aromatic hydrocarbon which containsalkyl substituents positioned so that steric hindrance would prevent orgreatly reduce the possibility of alkylation with the particular olefinshould not be subjected to the process. Examples of particularlysuitable aromatic hydrocarbons are benzene, toluene, xylene,trimethylbenzenes, and the other alkyl analogues, such as propyl andbutyl; the naphthalene aromatic hydrocarb ns. such as the mono anddi-substituted methylnaphthalenes.

The isoparafiin reactant is defined as a paraflinic hydrocarbon whichhas a tertiary hydrogen atom, i. e., parafiins which have a hydrogenatom attached to a tertiary carbon atom. Examples of these areisobutane, isopentane (2-methylbutane), 2-methylpentane, Z-methylhexane,B-methylhexane, 2,3-dimethylbutane (di-isopropyl) and2,4-dimethylhexane. Thus the isoparafiins usable as one reactant in theprocess contain from 4 to 8 carbon atoms.

In the isoparaffin-olefin system, the alkylation reaction is morefavored as the mole ratio of isoparaffin to olefin increases. Ingeneral, the isoparafiin to olefin mole ratio in the hydrocarbon chargeshould be at least 1. More than this amount is good and it is desirableto have an isoparafiin to olefin mole ratio between about 2 and 25 andin some cases more, for example, as much as 50. It is preferred tooperate with an isopatafiin to olefin mole ratio of between about and15.

The presence of non-reactive hydrocarbons in the hydrocarbon charge isnot detrimental unless the reactants become excessively diluted. Forexample, the isoparaflin may also contain isomers of the normalconfiguration. The olefins may contain paraffins of the same carbonnumber. Mixtures of 2 or more isoparatlins or 2 or more aromatichydrocarbons, or 2 or more olefins may be charged. In general, when aparticular product distribution is desired, it is preferable to operatewith a single isoparafiin and a single olefin, for example, technicalgrade isobutane and ethylene, both of about 95% purity.

The reactants may be mixed together before they are charged into thereactor. Or, they may be charged. into the reactor separately. Or, aportion of the olefin. may be blended with the isoparaflin or aromaticbefore introduction into the reactor and the remainder of the olefininjected into the reactor. The charge may be introduced all at. onepoint into the reactor or it may be introduced at 2 .or more points. Thealkylation reaction is somewhat exothermic and temperature control isfacilitated by introducing the olefin into the reactor at more than onepoint.

The BF member of the catalyst pair may be premixed with the isoparafiinand olefin before introducing these into the reactor but this should notbe done when an extremely reactive system such as isobutane andisobutylene or aromatic hydrocarbons and olefins are being used; or whenan olefin that is very rapidly polymerizable is being used. The BF maybe blended with the isoparafiin reactant and introduced into the reactorwith this member when the isoparaifin and the olefins are beingintroduced separately. The BF may also be introduced directly into thereaction zone independently from the hydrocarbons charged. The BF may beintroduced into the reactor at a single point or at several points tohelp control temperature and reaction rate.

The reactor may be a vessel providing for a batch-type reaction, i. e.,one wherein the desired amount of isoparaffin or aromatic and olefin arecharged to a closed vessel containing the catalyst pair and the vesselthen maintained at the desired temperature for the desired time. At theend of this time, the hydrocarbon product mixture and unreactedmaterials are withdrawn from the vessel and processed to separate thealkylate product from the unreacted materials and lower and highermolecular weight materials. The reactor may be a fixed bed operationwherein the reactants and freeBF are flowed through the bed of thehydrate salt member of the cat: lyst pair, the space velocity beingcontrolled so that th. desired amount of reaction is obtained during thepassag' of the reactants through the bed of hydrate salt. Under someconditions, a moving bed of hydrate salt may be utilized. In stillanother set of circumstances, a fluidized bed of hydrate salt may beutilized with the incoming stream of, reactants providing the energy forthe fiuidization of the solid hydrate salt. Other methods of operationcommon in the catalytic refining aspects of the petroleum industryutilizing solid catalyst may be readily devised.

It has been pointed out that the solid member of the catalyst pair isreally a complex of the salt hydrate and BF the BF apparently reactingwith the water of hydration. The complex may be preformed, by exposingthesalt hydrate to BF for a time sufficient to introduce some BF intothe solid component or even enough to complex all of the water ofhydration; this being done before the reactants are introduced into thereaction zone or even before the solid member of the catalyst pair ispositioned in the reaction zone. The complex may be formed in situduring a batch-type reaction. In the batch-type operation, it isconvenient to introduce all the BE, into the reaction vessel at once.This amount of BB, is: suflicient not only to complex with the water ofhydration but also provide the desired amount of free-8P In a fiowsystem, the solid member may be prepared in situ by charging freshhydrate salt to the re,- action zone and forming the complex during theinitial passage of reactants and BF over the salt hydrate. Somealkylation reaction occurs even though the salt hydrate has not taken upsufficient BF to complex all the water of hydration. As the flow ofreactants and BE, continues over the solid member, eventually the salthydrate will become saturated with respect to BF3. At this time, theamount of BF introduced into the reaction zone should be cut back tothat amount of free-BE, desired, under this particular set of operatingconditions.

The illustrative embodiment set out in the annexed.

figure forms a part of this specification. It is pointed out that thisembodiment is schematic in nature, that many items of process equipmenthave been omitted, since these may be readily added by those skilled inthis art and that this embodiment is only one of many which may bedevised, and that the invention is. not to be limited to, this,particular embodiment.

In the figure, it is desired to produce a high yield of di-isopropyl foruse as a blending material for gasoline. Ethylene from source 11 ispassed by way of line 12 into mixer 13. Liquid isobutane from source 14.is passed by way oflines. 16 and 17 into mixer 13.. Both the ethyl oneand the isobutane are about purity, the remainder being n-butane andethane, with trace amounts of other components found in materialsderived from petroleum refining sources. Mixer 13, in this instance, isa simple orifice-type mixer suitable for intermingling a liquid and agas, or two liquids. Recycle isobutane from line 18 is passed by way ofline 17 into mixer 13. In this embodiment, the molar ratio of isobutaneto ethylene is 6.

From mixer 13, the blend of isobutane and ethylene is passed by way ofline 19, through heat exchanger 21, where the temperature of the blendis adjusted to 30 C. The temperature of the blend leaving exchanger 21is somewhat lower than the reaction temperature, since there is a heatrise in the reactor due to exothermic reaction. From exchanger 21, thestream of isobutane and ethylene is passed by way of lines 22 and 23into the top of reactor 24.

Boron trifiuoride is passed from source 26 by way of valved line 27 andline 28 into line 23, where it meets the stream of isobutane andethylene. It desirable, a mixer may be introduced into line 23 to insurecomplete intermingling of the BF and the hydrocarbon charged. Recycle B1is introduced from line 29 by way of lines 28 and 23. In thisembodiment, the salt hydrate is completely complexed with respect to B1and only the necessary freeBF is introduced by way of line 28. Theweight ratio of free-B1 from line 28 to ethylene present in line 23 is1.1.

Reactor 24 is shown as a shell and tube type vessel. Hydrate salt iscontained in the tubes 31. The alumina balls 32 and 33 are positionedabove and below the headers in the reactor to maintain the hydrate saltwithin the tubes. In order to maintain the temperature in the reactor atsubstantially 35 C., water is introduced into the shell side by way ofline 36 and is withdrawn by way of line 37.

In this embodiment, the reactor was charged with nickel silicomolybdatecontaining 1 mole of water of hydration per mole of silicomolybdate. Thehydrate salt was preformed into pellets about one-eighth inch indiameter and about one-eighth inch in height. Some silica was present toact as a lubricant in the extrusion of the pellets. The salt hydrate wascontacted with BP in an amount such that all of the water of hydrationwas complexed with B1 This operation was carried out before reactantswere introduced into the reactor. The reactor pressure was maintained at600 p. s. i. This permits maintaining the isobutane and substantiallyall of the ethylene in the liquid state.

The product hydrocarbon mixture is passed out of reactor 24- by way ofline 41. This stream contains the alkylate product, unreacted isobutane,a small amount of unreacted ethylene and pentanes as well as BF Thestream from line 41 is passed into gas separator 42 where the BFisobutane, some pentanes and some alkylate product are taken overhead byway of line 43. The material taken overhead from the separator 42 ispassed into fractionator 44.

Fractionator 44 is adapted to separate the BF as a gas, the isobutane asa liquid and the higher boiling materials as a bottoms product.Fractionator 44 is provided with an internal reboiler 46 and an internalcondenser 47. BF and unreacted ethylene are taken overhead fromfractionator 44 by way of line 48 and may be passed out of the system byway of valved line 49. The material from line 49 may be periodicaliypassed to a B1 purification operation to remove non-condensablc inertgases which build up in the system. Ordinarily the stream from line 48is recycled by way of valved lines 29 and lines 28 and 23 to reactor 24.

Isobutane is withdrawn as a liquid stream by way of line 51 and isrecycled by way of lines 18 and 17 to mixer 13 for reuse in the process.Bottoms product from fractionator 44 is withdrawn by way of line 52 andmay be passed to storage or further processing by way of valved line 53.This stream from line 52 consists substantially of isopentane. Someunsaturated C hydrocarbons are also present and also a small amount ofhigher boiling alkylate material.

The liquids separated in gas separator 42 are passed by way of line 56into fractionator 57. The bottoms product from fractionator 44 may bepassed by way of valved line 58 and line 56 into fractionator 57 forcomplete removal of the alkylate material. In this embodiment, thebottoms are passed to fractionator 57.

Fractionator 57 is provided with an internal reboiler 58 and is adaptedto produce the desired alkylate products from the hydrocarbon productmixture entering from line 56. A vapor stream is taken overhead by wayof line 61, is condensed in cooler 62 and is passed to storage by way ofline as. The material from line 63 consists substantially of isopentaneand some unsaturated C material. This material may be used as a high octane blending stock for the production of motor gasoline of the desiredvolatility characteristics.

The alkylate product herein is considered to be that boiling above thepentane range and boiling below the maximum temperature usable in motorgasoline. In general, a 415 F. endpoint alkylate is biendable into motorgasoline without adverse effect in a specification calling for a 400 F.gasoline endpoint. Thus the allcylate product is considered to be thematerial boiling between about the lower limit of the hexane range and415 F. in the ASTM distillation procedure.

A considerable difference exists between the octane number of the Cfraction of the alltylate product and the higher boiling material. The Cfraction, which boils from about 110 to 170 F., has an F-l octane numberof lOl. The C material has an octane numberwhich ranges between about 75and 85, depending somewhat on the rractionation.

Light allryiate, which includes all the C material and some of the Cmaterial, is withdrawn from fractionator 57 by way of line 66. Heavyalkylate, which includes most of the Cr, and material boiling up to 415F. is withdrawn from fractionator 57 by way of line 67. A small amountof higher boiling bottoms is withdrawn by way of line 68.

In general, the C fraction of the alkylate product will contain fromabout 86 to about 90 mole percent of diisopropyl (2,3-dirnethylbutane).2-methylpentane and 3- metnyipentane represent substantially theremainder of the C product. Generally, only trace amounts of nhexane arepresent.

in Table 1 there are set out results in the testing of hydrates by meansof batch operation. In these runs, the tests were carried out under whatare more or less standard conditions, namely, a 4-liter carbon steelbomb was dried overnight in a stream of hot air at C. The hydrate to betested (90 grams) was charged to the bomb as a powder and the bomb wasevacuated. One kilogram of a dry blend of ethylene and isobutane wasadded and then B1 (90 grams) was pressured in. The charged bombs wereplaced in a rocker and allowed to rock for 20 hours. At the end of thistime a liquid sample was drawn through a bomb containing activatedalumina (to remove dissolved 8P and hydrate particles). This san1- plewas submitted for Podbielniak distillation. A C cut from the Podbielniakdistillation was analyzed by mass spectrometer. In some cases aftersampling, the remaining major portion of the product was debutanized onan Oldershaw column and then fractionated on a packed column.

In run No. 1, the operation was carried out as described above exceptthat no salt was present in the bomb. The results show that only 34% ofdepentanized alkylate product was obtained by the use of BF alone as thecatalyst. Run No. 2, carried out with nickel silicomolybdate containingwater of hydration produced 116% of alkylate based on ethylene charged.Run No. 3, wherein silicomolybdic acid containing water of hydration andBF Were present, produced a depentanized alkylate product yield of farless than the BF alone.

TABLE I Run No 1 2 3 Nickel Silico- Hydrate None Silico- Inolybdicmolybdate Acid Conditions:

Isobutane/Ethylene (molar) 3. 2. 9 2.1 Hydrocarbon/Salt (Weight) 11.611.2 BFq/Ethylene (weight) 0.7 0. 8 0.6 Time. Hours 20 20 Temperature, O.s. -35 25-30 25-30 Pressure (Range), p. s. i. g- 300 260-190 328-Results:

Alkylate (Depentanlzed) 1 (wt.

percent Pentanes 0 22 0 Hexanes 7' Z 66 i 10 07+ 13 0 Total 34 1:16 10Ethylene Converted, Percent 73 hydration in said salt, at a temperaturebetween about -30 C. and a temperature substantially below thetemperature at which said hydrate salt decomposes, and at a pressuresufficient to maintain a substantial portion'of said reactants in theliquid state, and separating a hydrocarbon product mixture containingalkylate product v of said feed hydrocarbon and said olefin.

2. An alkylation process wherein an isoparafiin having from 4 to 8carbon atoms and an olefin having from 2 to 12 carbon atoms arecontacted, in a molar ratio of isoparafiin to olefin between about 2 and50, at a temperature between about 20 C. and 150 C. and a pressurebetween about and 2000 p. s. i., said pressure being at least sufficientto keep a substantial portion of said reactants in the liquid state, fora time sufficient to permit an appreciable amount of alkylation reactionto take place, in the presence of a catalyst comprising essentially (i).a nickel silicomolybdate containing water of hydration, and (ii) borontrifiuoride, said BF being present in an amount in excess of one moleper mole of hydrate water present in said salt, removing a producthydrocarbon mixture from said contacting zone and an alkylatehydrocarbon product is separated from said mixture.

3. The process of claim 2 wherein said isoparaffin is isobutane.

4. The process of claim 2 wherein said isoparafiin is di-isopropyl.

5. The process of claim 2 wherein said olefin is ethylene.

6. The process of claim 2 wherein said olefin is propylene tetramer.

7. The process. of claim 2 wherein the BF;,- is present in an amount, inexcess of 1 mole per mole of hydrate water, such that the free-B1 toolefin weight ratio is between about 0.2 and 1.5.

8. An alkyl'ation process which comprises contacting isobutane andethylene in a molar ratio of isobutane to ethylene between about 2 and25 at a temperature between about 15 C. and 100 C. at a pressure betweenabout 200 and 1000 p. s. i., said pressure being sufiieient to keep asubstantial portion of said reactants in the liquid state for a timesufficient to permit an appreciable amount of alkylation reaction totake place, in the presence of a catalyst pair comprising essentially(a) a salt- BF complex consisting of nickel silicomolybdate containingwater of hydration, and about 1 mole of BF;, per mole of hydrate waterpresent in said salt and (b) boron trifluoride in an amount such thatthe weight ratio of free-BF to ethylene charged is at least about 0.2,removing product hydrocarbon mixture containing alkylate product fromsaid contacting zone and separating alkylate hydrocarbon product fromunreacted isobutane and ethylene.

9. The process of claim 8 wherein said free-BF /ethyleneweight ratioisbetween about 0.35 and 1.

References Cited in the file of this patent UNITED STATES PATENTS2,301,966 Michel et a1. Nov. 17, 1942 2,376,119. Bruner et a1. May 15,1945 2,390,835 Hennion et a1. Dec. 11, 1945 2,425,096 Ipatieff Aug. 5,1947 2,608,534 Fleck Aug. 26, 1952

1. AN ALKYLATION PROCESS COMPRISES CONTACTING (A) AN ALKLYATABLE FEEDHYDROCARBON FROM THE CLASS CONSISTING OF (1) ISOPARAFFIN HAVING FROM 4TO 8 CARBON ATOMS AND (2) AROMATIC HYDROCARBON AND (B) AN OLEFIN HAVINGFROM 2 TO 12 CARBON ATOMS, IN THE PRESENCE OF A CATALYST COMPRISINGESSENTIALLY (I) A NICKEL SILICOMOLYBDATE CONTAINING WATER OF HYDRATION,AND (II) BF3, SAID BF3 BEING PRESENT IN AN AMOUNT IN EXCESS OF ABOUT 1MOLE PER MOLE OF WATER OF HYDRATION IN SAID SALT, AT A TEMPERATUREBETWEEN ABOUT